1. Field of the Invention
The present invention relates to a switching power supply unit configured to produce switching output, the switching output being obtained by switching a DC input voltage, at an output winding of a power conversion transformer.
2. Background Art
Various types of DC/DC converters have been proposed for a switching power supply unit, and provided for practical use in the past. Most of the DC/DC converters are in a type where a DC input voltage is switched by switching operation of a switching circuit connected to a primary winding of a power conversion transformer (transformer), and the switching output is produced at a secondary winging of the power conversion transformer. A voltage induced in the secondary winging with switching operation of the switching circuit is rectified by a rectifier circuit, then converted into a DC voltage by a smoothing circuit, and then outputted.
In such a switching power supply unit, when a plurality of rectifier circuits are used for the purpose of controlling voltage drop in a rectifier circuit or a smoothing circuit to be small in order to handle a large current, a smoothing circuit using an LC circuit needs to be used to balance currents flowing from the respective rectifier circuits so as to stabilize output. Thus, for example, U.S. Pat. No. 6,362,986 proposes a switching power supply unit, in which an inductor having two magnetic cores is used, so that magnetic fluxes generated by currents flowing from the respective rectifier circuits are balanced.